The present invention relates to a method and apparatus for introducing a cable into a vulcanization chamber.
The invention is applicable to any type of cable manufacture in which a circular or sector-shaped conductor is passed through an extruder, where it is surrounded with a layer of crosslinkable plastic, such as for example crosslinkable PE or crosslinkable rubber, e.g. EPDM-rubber and is subsequently introduced into a vulcanization chamber in which crosslinking takes place. In the case of multilayer cables, the conductor can also be passed through a plurality of extruders. Crosslinking in the vulcanization chamber takes place continuously, so that such chambers are also called the "CV-zone." Crosslinking takes place by conversion by means of a heat transfer medium, e.g. vapor, particularly water vapor, by oil or by gas.
In the known continuous crosslinking process, it is standard practice for the vulcanization chamber to be fixedly connected with the extruder head. However, this has the disadvantage that the extruded cable can only be observed when it has left the vulcanization chamber and the necessary corrections to the extruder settings can only be performed after the transit time which is dependent on the pipe section length, the cable dimensions and the nature of the heat transfer, which can take up to an hour or more.
Attempts have been made to overcome this disadvantage by measuring/technical determinations of the cable geometry by means of incorporated measuring devices operating with X-rays.
The direct connection of the vulcanization section to the extruder head provides certain advantages from the sealing standpoint, in that a seal is only required at the outlet from the vulcanization chamber and serves to prevent the outflow of the heat transfer medium. It is also known to arrange such a seal at the inlet to the chamber (DOS No. 2,626,721), so that the vulcanization chamber is separated from the extruder. At this point, a sealing liquid is used, the disadvantage being that for sealing gaseous or vaporous media, the cable must be turned, being guided away from the extruder with an upward inclination and then the cable must be turned again back in the pressure system inlet of the vulcanization chamber.